I once wrote some low-quality article about my setup using a T400 Thinkpad, but I thought I would give a little advice to anyone thinking about purchasing one.
My philosophy of computer hardware is as follows: 2 or more cores, 64-bit, solid-state drive. This is par for an acceptable experience using modern browsers, and consooming content. A decent gpu helps a lot too.
So I can easily recommend against any of the 32-bit Thinkpads, as well as any that are single core cpus. I have an X60, but its hard to use in 2022. The T400 is a well-built workhorse and will serve most people's needs fine, but I must stress that the GMA 4500MHD graphics on it are absolute trash. The poor thing struggles to play classic DOOM at low resolutions. If you don't need 3D acceleration or high resolutions, the T400 is just fine.
But why not step up a little to the X220? Since it is either an Intel i5 or i7, you can expect very good performance for its age. It handles 1080p relatively well with its Intel HD 3000 graphics, and having those extra cpu threads really helps in compiling software.
If Thinkpads interest you, this is probably why. The Thinkpads I have mentioned so far can be flashed with a modified BIOS to remove or at least neuter the Intel Management Engine. Many of the Thinkpads using Core 2 Duo cpus can be librebooted, osbooted, or corebooted. The models using i5s or i7s can only be corebooted, and you generally have to compile the roms yourself.
Should you libreboot? Absolutely not. A librebooted Thinkpad is effectively no more secure than an osbooted or corebooted Thinkpad in terms of microcode, but one may argue that the total removal of the Intel ME on the Core 2 Duo Thinkpads is more secure. Regardless, I don't recommend libreboot, because once I flashed osboot, my T400 ran so much better.
Should you osboot? Up to you. Consider it coreboot without the hassle of compiling your own rom, but with fewer machines available at the moment. Choose this over libreboot at the very least.
Should you coreboot? If you don't mind reading lots of documentation and guides, and don't mind risking bricking your Thinkpad, go for it. I corebooted my X220 myself with no issues at all, and if you get stuck, there's probably a guide out there for whatever machine you have. If you can compile your own software, you can handle compiling coreboot. If you go this route, you probably should compile on a powerful machine, otherwise it will take forever to finish.
Since I can only speak effectively from experience, I will mention the Thinkpads that I own.
My highest recommendation goes to the X220. Its small, sleek, yet still powerful enough to get the job done in 2022. If you can get the i7 model, I hear it even has 1 USB 3.0 port. It also has the classic tactile keyboard. This is my current machine; it is docked with a mouse, keyboard, and 1080p monitor attached. It can also handle light gaming if you can't quite kick the habit like me. It plays classic DOOM at 1080p okayish, and Cataclysm: Dark Days Ahead great. I haven't tried many other games, but if you mostly play old boomer shooters and ASCII games that require ever increasing doses of prescription medication, it will probably run them just fine. Coreboot it, and you'll have a great little laptop.
The T400, being a Core 2 Duo and using the godawful GMA 4500MHD, is not going to be the fastest experience (especially without microcode). That being said, its still perfectly usable as long as you don't need high resolution, and you have a little patience. Web browsing can be a little slow; I think the gpu is to blame. Still, it runs CDDA great so I can only complain so much. While it can be librebooted, use either osboot or coreboot as stated earlier.
Most if not all of these are only 32-bit, so don't bother. I think some T60 laptops are 64-bit though if you don't mind a laptop from the Bush II administration. If you must have an X60 however, it can be librebooted, osbooted, or corebooted.
Just kidding, absolutely don't get this one. Its a Pentium 4 which is not only 32-bit, but agonizingly slow. I must admit though, it is an arousing Thiccpad. If for some reason you want to play around with such an old machine (or old machines in general), look into plop boot manager.
My ultimate recommendation is to bite the bullet and get those Thinkpads that have i5 or i7 cpus like the X220 or T420 among others. Make sure they can be corebooted, slap in an SSD and a free software wifi chip, and you'll barely notice that you're using a 10 year old computer. If you don't mind being a little slower, the Core 2 Duo laptops like the T400 or X200 are great for their age; give them an SSD and either coreboot or osboot and they'll be fine. Avoid any 32-bit machines. If you want truly pornographic detail about every Thinkpad, check out Thinkwiki.
Latitude 6430s. There's a trackpoint, it just hard to see.
Contrary to silly memes on the internet, Thinkpads were not the only bulletproof laptops around 10 years ago. I can just as easily recommend the older Dell Latitudes, because they were generally targeted at government and education users. My first cousin-once-removed brought me his old US Census laptop that was a 13 year old Latitude, and I'm willing to bet it could hold its own against a brick wall. I have also sold slightly newer ones I got from state surplus that were quite rugged, if a bit heavy. As a nice bonus, the 10 to 15 year old Latitudes have keyboards and Trackpoints that rival the Thinkpads.
The only drawback to the Latitudes is that I don't think there are custom BIOS options available for them, but that doesn't mean we can't have a glowboy free Latitude. I haven't tried it myself yet, but I think if I extracted the machine's BIOS, used me_cleaner on the rom, then flashed back the modified image, the machine would be NSA backdoor free. If you use this on an i5 or i7, it will severely handicap the ME, but on an older Core 2 Duo it will totally delete the little devil.
These are the best built laptops I have experience with, but maybe there are others I'm not familiar with. If you know of other brickhouse-tough laptops, send me an email.
It probably runs TempleOS.